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Picturing the radiation?
On antennae that are several half-wavelengths long (beverage, Rhombic, etc)
what does the radiative wavefront look like when close to the antennae, even though it is presented in the literature as a plane wave further out? The reason that I ask is the on such longwires, there are parts of the wire which will be radiating positively, and parts negatively, thereby suggesting that the outgoing wave, spherical though it might be, has a +/- modualtion were you to travrse its circumference? |
Picturing the radiation?
gareth wrote:
On antennae that are several half-wavelengths long (beverage, Rhombic, etc) what does the radiative wavefront look like when close to the antennae, even though it is presented in the literature as a plane wave further out? Run just about any version of NEC and look at the near field data and find out. The reason that I ask is the on such longwires, there are parts of the wire which will be radiating positively, and parts negatively, thereby suggesting that the outgoing wave, spherical though it might be, has a +/- modualtion were you to travrse its circumference? Are you attempting to say the pattern has lobes in as many words as possible? Shape of the wavefront tells you little about the workings of an antenna as an antenna as it depends on things like the emitter area and distance from the emitter. Example: Sunlight from the Sun has a spherical wavefront, but at the Earth's distance of 150,000,000 kilometers you are hard pressed to measure the difference from planar. -- Jim Pennino |
Picturing the radiation?
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Picturing the radiation?
On Tue, 14 Oct 2014 21:34:52 +0100, "gareth"
wrote: On antennae that are several half-wavelengths long (beverage, Rhombic, etc) what does the radiative wavefront look like when close to the antennae, even though it is presented in the literature as a plane wave further out? I've never bothered to grind out this calculation, so you've gotten my attention. If you find the assumptions insufficiently precise, perhaps some back of the envelope math might be useful. If you have a point source radiator, spewing RF at a wavelength = x, where the wavefront peaks are x distance apart, how large a radius in the form n * x would you need to have before the wavefronts are essentially a straight line? In other words, how many wavelengths would you need to be away from the RF source before the wavefront is essentially a straight line? Obviously, the wavefront will never be completely straight, but I would guess(tm) that the wire diameter of a typical 0.5 wave wire dipole receive antenna should be sufficiently small to be considered straight. Unfortunately, that dimension makes the calculation frequency dependent, so I'll just assume 10 MHz and #14 AWG antenna to make the math easier. 0.5 wave at 10 MHz = 15 meters Dia of #14 AWG wire is about 1.63 mm. The calcs are a bit too messy to show in ASCII, so I scanned my scribbling: http://802.11junk.com/jeffl/crud/wavefront.jpg At 10 MHz and a distance of 14.9 km (9.3 miles) the wavefront has straightened out sufficiently so that the arc is no wider than the width of a #14 AWG antenna wire. You would be hard pressed to keep your receive antenna straight within the diameter of a #14 AWG wire, so this degree of accuracy is massive overkill. The reason that I ask is the on such longwires, there are parts of the wire which will be radiating positively, and parts negatively, thereby suggesting that the outgoing wave, spherical though it might be, has a +/- modualtion were you to travrse its circumference? Are you familiar with the term "word salad"? I'm sure you're trying to convey a question, but it's difficult to find it under all the misplaced and misused technical terms. A Beverage, Rhombic, etc is not the same as a longwire. Antennas radiate AC and therefore do not have the + and - polarity of a DC power source. The radiation pattern from a long wire is not spherical (isotropic). Nothing in the antenna affects the modulation. Traversing a circumference results in the diameter. Kindly spend some time looking up the definitions of the terms you use so that I don't have to decode your intentions. Back to hauling firewood up the hill... -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Picturing the radiation?
"gareth" wrote in message ... On antennae that are several half-wavelengths long (beverage, Rhombic, etc) what does the radiative wavefront look like when close to the antennae, even though it is presented in the literature as a plane wave further out? The reason that I ask is the on such longwires, there are parts of the wire which will be radiating positively, and parts negatively, thereby suggesting that the outgoing wave, spherical though it might be, has a +/- modualtion were you to travrse its circumference? Parts of the wire have negative radiation? Outgoing wave has circumferential modulation? OK, I get it now. You aren't being serious. |
Picturing the radiation?
"Brian Reay" wrote in message
... If you follow his 'theory' through, try applying it to light (which follows the same laws of physics). Basically, he is confused. Once again, Brian,the origination of abuse comes from you. |
Picturing the radiation?
"Brian Reay" wrote in message
... He is confusing the E and M fields, which have a sine form but in orthogonal planes, for 'the radiation', in essence he doesn't understand the nature of an EM wave. Once again, Brian, the origination of abuse comes from you, and yet you don't know enought yourself to discuss the matter, so you do not. |
Picturing the radiation?
On Wednesday, October 15, 2014 4:18:22 AM UTC-5, gareth wrote:
"Brian Reay" wrote in message ... If you follow his 'theory' through, try applying it to light (which follows the same laws of physics). Basically, he is confused. Once again, Brian,the origination of abuse comes from you. Who cares.. This is not some silly abuse encounter group.. :/ Did you do what was suggested and run it through a program? That will totally answer your question and you can see it visually. You can download this program, and there are already beverage ant files ready to go. Even a caveman could do it. It's free, and good nuff for gov work. And it will handle a lot of segments for the more complex antennas. The beverages are under the "receive" antenna folder.. http://hamsoft.ca/pages/mmana-gal.php |
Picturing the radiation?
wrote in message
... This is not some silly abuse encounter group.. No? ... Did you do what was suggested and run it through a program? Even a caveman could do it. .... and now, yes? |
Picturing the radiation?
On Wednesday, October 15, 2014 4:36:06 AM UTC-5, gareth wrote:
wrote in message ... This is not some silly abuse encounter group.. No? ... Did you do what was suggested and run it through a program? Even a caveman could do it. ... and now, yes? Well, I guess you know the answer to your question now. Yes? |
Picturing the radiation?
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Picturing the radiation?
On Wednesday, October 15, 2014 12:20:12 PM UTC-5, Brian Reay wrote:
It is really best not to respond to him directly, you will notice I never do. If you ignore him, he eventually 'blows his top' and goes off to sulk. No worries. I enjoy toying with these types. It's good wholesome fun for the whole family. :) I'm pretty much convinced he's one of Art Unwin's long lost UK relatives. :| Their tactics and brand of bafflegab are quite similar. |
Picturing the radiation?
"Brian Reay" wrote in message
... You need to appreciate that Gareth considers anyone who corrects him as being abusive. Untrue, but you take every opportunity to be abusive to me, as above. Having seen him in action many, many times, I can assure you this is so and point you are countless examples in the uk.r.a and other newsgroup archives. Untrue. He invariably uses a similar technique and ends up using the same abusive terms (eg 'Silly Boy'). Untrue. He has been doing this for well over a decade, he was using the same techniques before I started using uk.r.a in around 2000. Untrue. It is really best not to respond to him directly, you will notice I never do. If you ignore him, he eventually 'blows his top' and goes off to sulk. Untrue. |
Picturing the radiation?
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Picturing the radiation?
On 10/14/2014 7:32 PM, Jeff Liebermann wrote:
Back to hauling firewood up the hill... You are doing it wrong. You will find it much easier to haul the firewood down the hill. -- Rick |
Picturing the radiation?
On Wednesday, October 15, 2014 5:14:20 PM UTC-5, rickman wrote:
On 10/15/2014 2:03 PM, wrote: On Wednesday, October 15, 2014 12:20:12 PM UTC-5, Brian Reay wrote: It is really best not to respond to him directly, you will notice I never do. If you ignore him, he eventually 'blows his top' and goes off to sulk. No worries. I enjoy toying with these types. It's good wholesome fun for the whole family. :) I'm pretty much convinced he's one of Art Unwin's long lost UK relatives. :| Their tactics and brand of bafflegab are quite similar. And Gareth enjoys you toying with him... I hope that didn't sound too much like a sexual metaphor. It had been my intention to totally ignore you.. Remember? You know the other day when your silly ass was trying to hump my legs? But here you are again.. Trying to fondle my trouser trout without using your fingers... :+ I'm not aroused. |
Picturing the radiation?
On Wed, 15 Oct 2014 18:25:14 -0400, rickman wrote:
On 10/14/2014 7:32 PM, Jeff Liebermann wrote: Back to hauling firewood up the hill... You are doing it wrong. You will find it much easier to haul the firewood down the hill. My cardiologist demands that I get more exercise. Schlepping firewood up about 50 step is quite good a producing the desired effect. That which doesn't kill me makes me stronger. I could easily install a cable lift, bucket hoist, or conveyor belt to move the firewood up the hill with less exertion. However, I won't do that. Other than occasional bicycling and fast walks, firewood schlepping is my major form of exercise. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Picturing the radiation?
On 10/15/2014 8:36 PM, Jeff Liebermann wrote:
On Wed, 15 Oct 2014 18:25:14 -0400, rickman wrote: On 10/14/2014 7:32 PM, Jeff Liebermann wrote: Back to hauling firewood up the hill... You are doing it wrong. You will find it much easier to haul the firewood down the hill. My cardiologist demands that I get more exercise. Schlepping firewood up about 50 step is quite good a producing the desired effect. That which doesn't kill me makes me stronger. I could easily install a cable lift, bucket hoist, or conveyor belt to move the firewood up the hill with less exertion. However, I won't do that. Other than occasional bicycling and fast walks, firewood schlepping is my major form of exercise. Yes, "that which doesn't kill me". I doubt hauling firewood uphill is what your doctor would recommend. You should find the time to bicycle more. -- Rick |
Picturing the radiation?
rickman wrote in :
Yes, "that which doesn't kill me". I doubt hauling firewood uphill is what your doctor would recommend. You should find the time to bicycle more. I find that cross country running helps with sciatica, so long as there is no heavy jarring of my spine. So I have to be careful of that, but the result proves the old 'use it or lose it' strategy. |
Picturing the radiation?
On 10/16/2014 3:33 AM, Lostgallifreyan wrote:
rickman wrote in : Yes, "that which doesn't kill me". I doubt hauling firewood uphill is what your doctor would recommend. You should find the time to bicycle more. I find that cross country running helps with sciatica, so long as there is no heavy jarring of my spine. So I have to be careful of that, but the result proves the old 'use it or lose it' strategy. I know running has some issues which may or may not be a problem for any given person. I discovered kayaking a few years ago and found it is a fantastic way to exercise. It really builds the core muscles... you know, the ones everyone says you need to strengthen. It helped me so much that my back pain I've had off and on since I was 30 is pretty much all gone now. It is true what they say about strengthening those muscles. Too bad I can't do it year 'round here. I need a summer place in Florida. -- Rick |
Picturing the radiation?
rickman wrote in :
I know running has some issues which may or may not be a problem for any given person. I discovered kayaking a few years ago and found it is a fantastic way to exercise. It really builds the core muscles... you know, the ones everyone says you need to strengthen. It helped me so much that my back pain I've had off and on since I was 30 is pretty much all gone now. It is true what they say about strengthening those muscles. Too bad I can't do it year 'round here. I need a summer place in Florida. Nice. I've kayaked for only a short time on a couple of occasions (on calm sunlit sea, and in a grey force 7, off the Pembrokeshire coast) but I liked it. What I really miss is sailing... Not so arduous, but the balance of intensity and space to just sit and be aware of it all makes me know why it is some people's whole life. I'd like to do that again. |
Picturing the radiation?
"Brian Reay" wrote in message
... He is confusing the E and M fields, which have a sine form but in orthogonal planes, for 'the radiation', in essence They are not planar, but 3D fields. he doesn't understand the nature of an EM wave. Physician, heal thyself. |
Picturing the radiation?
"Brian Reay" wrote in message
... It is really best not to respond to him directly, you will notice I never do. So, you're brave enough to shout out your insults from behind the safety of the kindergarten fence, but too cowardly to deal with the responses to you? |
Picturing the radiation?
On Fri, 17 Oct 2014 09:43:13 +0100, gareth wrote:
"Brian Reay" wrote in message ... It is really best not to respond to him directly, you will notice I never do. So, you're brave enough to shout out your insults from behind the safety of the kindergarten fence, but too cowardly to deal with the responses to you? But, but, but, that's what you are doing, as you know that he's not going to respond to you. It's why these deranged, borderline hysterical, illogical conclusions of yours are going unchallenged. But you already knew that... |
Picturing the radiation?
gareth wrote:
"Brian Reay" wrote in message ... He is confusing the E and M fields, which have a sine form but in orthogonal planes, for 'the radiation', in essence They are not planar, but 3D fields. QED he doesn't understand the nature of an EM wave. -- Jim Pennino |
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